Internal combustion free piston engine



Sept. 13; 1960 A. BRAUN 2,952,251

INTERNAL COMBUSTION FREE PISTON ENGINE Filed Aug. 12, 1957 2e jtyalo INVENTOR flnian ,8 ran n ATTORNEY United States Patent O INTERNAL COMBUSTION FREE PISTON ENGINE Anton Braun, 437A Johnson St., Kingston, Ontario, Canada Filed Aug. 12, 1957, Ser. No. 677,542

3 Claims. (Cl. 123-46) This invention relates to. internal combustion free piston engines.

Generally speaking, a free piston engine comprises a power cylinder located in concentric relation with and between compressor cylinders and/or bounce cylinders, and respective pistons in such cylinders. The power pistons operate in an opposed reciprocating manner and each carries with a compressor and/or bounce or cushion piston which is an integral part of the power piston and of enlarged diameter. The operation of the two power pistons, in order to maintain them in constrained relative motion, is synchronized by means such \as a rack and pinion, parallelogram linkage, rocker arms, or the like.

There are several disadvantages in the structural arrangements of conventional free piston engines.

One such disadvantage resides in the fact that a number of stufling boxes and/ or seals are required in order to keep the compression or cushion part separated from the air receiver, atmosphere, and other parts of the engine.

Another disadvantage lies in the fact that part of the heat generated in the engine part is transmitted to the compressor and cushion parts of the pistons and, as the compressor parts of the pistons are always under compressed or partly compressed high temperature air, they heat up considerably which results in lower possible compression ratios, higher strain on liners, piston rings, and the engine in general, and lower volumetric efiiciency with larger dimensions. i

Leaks in the previously mentioned seals and stuffing boxes have resulted in lubricating oil explosions. Moreover, the seals and stuffing boxes employed in connection with the synchronizing mechanism require considerable attention to avoid loosening, leaking, and undue tightness which might result in seizing up.

An object of the present invention is to provide a free piston engine in very simple and compact form which avoids the mentioned drawbacks of conventional engines,

which is easily accessible in all its parts, and which re-.

quires no stufling boxes.

In a broad aspect, the invention resides in a free piston engine comprising a power cylinder, a pair of compressor cylinders, a pair of power pistons in opposed reciprocating relation in said power cylinder, each said power piston having a compressor piston of enlarged diameter connected thereto and reciprocatably mounted in one of said compressor cylinders, the two confronting faces of said compressor pistons being open to the atmosphere whereby on inward movement of said compressor pistons towards each other no compression is efiected thereby.

Other objects, details, and advantages of the invention will become apparent as this description proceeds with particular reference to the accompanying drawing, in which:

Figure 1 is a sectional side elevation of a free piston engine in accordance with the invention,

of another form engine showing an actuating means for accessory mechanisms.

In the drawing, 1 is a power cylinder and 2 and 3 compressor cylinders axially arranged with respect to the power cylinder one at each end thereof, the compressor cylinders being of larger diameter than that of the power cylinder, all in accordance with conventional practice.

The compressor cylinders are connected together by a central frame member 4, an aligning disc 5 being interposed between the adjacent end of each cylinder 2 and 3 and the frame member 4. As shown, annular shoulders 6 on the disc 5 receive the flanged ends of cylinder 2 or 3 and member 4, the assembly being secured together as by bolts, not shown. A shouldered end portion 7 on the cylinder 1 extends into an axial opening in each disc 5. There has thus been provided a simple means of concentrically aligning the two compressor cylinders 2 and 3 with the power cylinder 1, which may be supported by the discs 5 with a light press fit therein and which requires no other means to connect it structurally to other parts of the engine. Each disc 5 has a plurality of openings 8 providing communication between the interior of cylinders 2 and 3 and atmosphere. In other words, the inner end of each cylinder 2 and 3 is open to atmosphere.

Opposed power pistons 9 and 10 are reciprocatingly mounted in cylinder 1 and each such piston has fixed to its outer end a compressor piston 11 or 12 of larger diameter for reciprocation in the compressor cylinders 2 and 3. Each piston 11 and 12 has therein a plurality of valves 13 of conventional type which open on the inward stroke of the piston but which are closed during the outward stroke of the piston.

The outer end of each cylinder 2 and 3 is provided with a closure plate 14 and a cover 15 which is spaced from the plate 14 to provide a passage 16 therebetween. Each plate 14 has, as shown, a shouldered edge portion which is received between flanged edge portions of cover 15 and respective cylinder 2 or 3, such assembled edge portions being secured together as by bolts, not shown. Each plate 14 is provided with-a plurality of valves 17 of conventional type and adapted to open under pressure of air within the compressor cylinder, i.e., on the outward stroke of the compressor piston, and to be closed following the outward stroke of such piston.

Stationary bounce pistons 18 and 19 are respectively mounted in hubs 20 of covers 15. Each hub 20 has its inner end supported in an axial opening in plate 14, through which the bounce piston 18 or 19 extends. As shown, each piston 18 and 19 is telescopically received in an axial recess 21 or 22 in the respective piston assemblies 9, 11 and 10, 12, it being apparent that the structure of plates 14 and covers 15 is such as to support the bounce pistons 18 and 19 in axial alignment with the power and compressor pistons. I

The power cylinder '1 is nozzle thereof. Power cylinder 1 also has a. series of circumferentially arranged inlet ports 24 spaced from its center line and adjacent that end-of the cylinder through which- V closer to the center ,line of.the cylinder 1 than are ports 24.

provided with a fuelinjection' 23 located substantially midway between the ends.

Compressed air delivered from cylinders 2 and 3 through valves 17 is led through passages 16 into ducts 26, thence through a tubular fitting 27 into an intake ring 28 enclosing ports 24, and from the latter into cylinder 1.

Exhaust gases from ports 25 flow into a ring 29 enclosing such ports and thence through an exhaust duct 34 Mechanism for synchronizing movement of the pistons may comprise, for instance, racks 31 and pinion 32. As shown, the racks 31 may conveniently extend through openings 8 in the discs 5, thus eliminating the need for seals or stuffing boxes. a

For the sake of clarity, the injection equipment, coolant and lubrication pumps, as well as the drives for this equipment, have been omitted from the drawing. Moreover, no specific cooling system has been shown. it will be apparent that the engine shown lends itself particularly well to an air cooling system although, of course, a liquid cooling unit could be employed.

Bounce pistons 18 and 19 may be provided with respective covers 33 and 34, which would permit internal liquid cooling thereof, or such covers may be omitted, as shown in Figures 2 and 3. Furthermore, each piston 1% and 19 may have an opening 35 in the head thereof, as shown in Figure 3, whereby internal air cooling of the compressor piston 3 may be effected.

As shown in Figure 4, a cam bar 36 may be carried by piston 2 and extending through an opening 8 in disc 5. The cam bar 36 is adapted to actuate a fuel-injection pump 37 to supply fuel to the injection nozzle 23. It will be apparent that the cam bar 36 may be employed for actuating other accessories such as lubricating and cooling pumps.

In operation, assuming that pistons 9 and 10 are in their innermost position, i.e., closest position to the injection nozzle 23, and that combustion of fuel is just taking place in the space or chamber formed by cylinder 1 and power pistons 9 and 10, such pistons 9 and 11) are thereupon forced away from each other in an expansion or power stroke. During such stroke, piston 1d will begin to uncover exhaust ports 25 a little in advance of uncovering of inlet ports 24 by piston 9 in order to provide necessary exhaust lead. Simultaneous movement of compressor pistons 11 and 12 will cause air from the cylinders 2 and 3 to flow through ports 24 into cylinder 1 for scavenging and recharging purposes, the exhaust gases being scavenged through ports 25. On the return stroke, after pistons 9 and 10 have closed ports 24 and 25, the compression stroke takes place until pistons 9 and 16 have again reached their innermost position. During the simultaneous return stroke of pistons 11 and 12, atmospheric air flows through valves 13 into the portions of cylinders 2 and 3 between the outer faces of pistons 11 and 12 and the plates 14. When a new fuel injection takes place, the entire cycle is repeated.

During the outward stroke of the pistons, the interior chambers formed by the recesses 21 and 22 constitute bounce cylinders in conjunction with the stationary bounce pistons 18 and 19 and thus result in a bounce cylinder compression stroke. The energy stored in this manner, together with the dead volume energy of the compressor parts, provides the necessary return energy to return pistons 9, 10 and 11, 12 to their innermost positions.

It will be apparent that the engine described operates with outward compression only, leaving one side of the compressor pistons open to ambient conditions. This arrangement results in several remarkable features. 7 Thus, it is no longer necessary to seal the synchronizermechanism against the atmosphere or other portions of the engine, as it is connected to the compressor piston on the side that is subject to ambient conditions. Stuffing boxes are therefore eliminated and the mechanism can be less precise dimensionally and thus more economically manufactured.

Furthermore, with one side of pistons 11, 12 open to atmosphere, and with outward compression, the inlet valves can be placed in the annular compressor sections of the pistons and the delivery valves in the compressor cylinder heads, leaving the compressor cylinders themselves free from valves, which results, in addition to the cooling of the one side of the compressor pistons, in a very effective cooling of the compressor liners and pistons, as well as simpler design, especially in the head region of the liners.

Moreover, with one side of pistons 11, 12 open to atmosphere, the engine accessories may be more simply and directly actuated as by cam bars attachedto the pistons on the side open to atmosphere. This arrangement provides more freedom structurally for location of accessories such as injection, fuel, lubrication and cooling pumps, and results in a more simplified sychronizing mechanism.

Another advantage of this arrangement is that the more critical inlet valves are subject to dynamic forces of the moving pistons in such a manner that the opening and closing periods of these valves can be effected by such forces in a very favourable manner.

By locating the intake valves in the pistons, the motion of the pistons during the intake period results in a pumping or blower-like action, which further supports favourably the air intake.

With outward compression the air delivery is arranged to occur at the time when the compressed air is needed for scavenging and charging of the power cylinder. Use can be made of the kinetic energy of the compressed air and the air can be carried to the engine intake ports through the simple duct shown, thus avoiding the usual air receiver around the center part of the engine and consequently leaving this part with power cylinder, synchronizer, injection equipment and the like, free and open and accessible for convenient observation and attention.

The arrangement described further results in a construction of very simple form which in turn reduces the tendency of deformation of important engine parts.

With an outward compression engine as described, most of the work of one cycle is done by the end of the outward stroke, thus requiring a small amount of return energy only which can be supplied by a relatively small size cushion or bounce piston and/or the dead-volume energy of the compressor stages.

=It will be apparent that the cushion or bounce pistons could be installed as integral parts of the power-compressor pistons and thus have the same motion as these p1stons.

In cases in which the bounce energy from the com pressor dead volume spaces is suflicient for the proper operation of the engine or a very small amount of extra bounce energy is needed only, the openings 35 in the stationary bounce pistons could be employed to apportion their function between bounce action and internal cooling of the power compressor-pistons.

With the stationary bounce pistons acting as such, inside the engine compressor pistons, the bounce pistons can be readily air or water cooled and so, due to their great relative temperature difierence, transfer of an appreciable amount of heat will take place from the enginecompressor pistons.

I claim:

1. An internal combustion free piston engine comprising a pair of longitudinally aligned compressor cylinders, an open frame connecting together the inner ends of said cylinders, a power cylinder of smaller diameter than that of said compressor cylinders located within said frame between said compressor cylinders and in axial alignment therewith, means supporting said power cylinder in said location comprising a pair of independent discs, each said disc having an axial opening, each end of said power cylinder being located in said axial opening of one of said discs and being in engagement with the wall of said axial opening, each said disc having its peripheral portion seated on the inner end of one of said compressor cylinders, each said disc constituting an inner end wall of one of said compressor cylinders and having a plurality of circumferentially spaced openings therein to place the inner end of said compressor cylinder in communication with atmosphere through said circumferentially spaced openings and said open frame, a pair of power pistons in opposed reciprocating relation in said power cylinder, each said power piston having a compressor piston of enlarged diameter connected thereto and reciprocatably mounted in one of said compressor cylinders, a closure plate closing the outer end of each said compressor cylinder, air outlet valves in each said closure plate and arranged to be closed on inward movement of said compressor pistons and to open on outward movement of said compressor pistons, a cover member forming a compressed air receiving passage enclosing the outer surface of each said closure plate and said valves therein, said power cylinder having an intake for scavenging and charging air, and a duct communicative between said passages and said intake, said intake receiving air solely from said passages through said duct.

2. An internal combustion free piston engine comprising a pair of longitudinally aligned compressor cylinders, an open frame connecting together the inner ends of said cylinders, a power cylinder of smaller diameter than that of said compressor cylinders located within said frame between said compressor cylinders and in axial alignment therewith, means supporting said power cylinder in said location comprising a pair of independent discs, each said disc having an axial opening, each end of said power cylinder being located in said axial opening of one of said discs and being in engagement with the wall of said axial opening, each said disc having its peripheral portion seated on the inner end of one of said compressor cylinders, each said disc constituting an inner end wall of one of said compressor cylinders and having a plurality of circumfer entially spaced openings therein to place the inner end of said compressor cylinder in communication with atmosphere through said circumferentially spaced openings and said open frame, as-pair of power pistons in opposed reciprocating relation in said power cylinder, each said power piston having a compressor piston of enlarged diameter connected thereto and reciprocatably mounted in one of said compressor cylinders, a closure plate closing the outer end of each said compressor cylinder, air outlet valves in each of said closure plate and arranged to be closed on inward movement of said compressor pistons and to open on outward movement of said compressor pistons, a cover member fixed to each said closure plate and forming an enclosed passage between said plate and said member for reception of compressed air through said valves in said plae, said power cylinder having an intake for scavenging and charging air, a duct leading directly from each said passage to said intake to supply said air, said passages being otherwise closed.

3. An internal combustion free piston engine comprising a pair of longitudinally aligned compressor cylinders, an open frame connecting together the inner ends of said cylinders, a power cylinder of smaller diameter than that of said compressor cylinders located within said frame between said compressor cylinders and in axial alignment therewith, means supporting said power cylinder in said location comprising a pair of independent discs, each said disc having an axial opening, each end of said power cylinder being located in said axial opening of one of said discs and being in engagement with the wall of said axial opening, each said disc having its peripheral portion seated on the inner end of one of said compressor cylinders, each said disc constituting an inner end wall of one of said compressor cylinders and having a plurality of circumferentially spaced openings therein to place the inner end of said compressor cylinder in communication with atmosphere through said circumferentially spaced openings and said open frame, a pair of piston assemblies each having a power piston and a compressor piston mounted in opposed reciprocating relation in said cylinders, said piston assemblies having an outward working stroke and an inward return stroke, each said power piston having a bounce chamber extending axially inwardly thereof from its outer end, a closure plate closing the outer end of each said compressor cylinder, air outlet valves in each said closure plate and ar ranged to be closed during said return stroke and to open during said working stroke, a cover member forming a compressed air receiving reservoir enclosing the outer surface of each said closure plate and said valves therein, each said compressor piston during said working stroke thereby acting to compress air in the portion of said compression cylinder between the outer face of said compressor piston and said closure plate, each said reservoir receiving said compressed air to store the same during said working stroke, said power cylinder having an intake for scavenging and charging air, the ducts leading directly from said reservoirs to said intake, said intake being closed by one of said power pistons and opened towards the termination of said working stroke for supply of scavenging and charging air to said power cylinder from said stored air in said reservoirs.

References Cited in the file of this patent UNITED STATES PATENTS 1,732,693 Pescara Oct. 22, 1927 2,897,674 Pescara Feb. 14, 1933 2,025,177 Pescara -Dec. 24, 1935 2,182,063 Steiner Dec. 5, 1939 2,189,497 Pescara Feb. 6, 1940 2,425,375 Kilchenmann Aug. 12, 1947 2,435,970 Lewis Feb. 17, 1948 2,462,745 Horgen Feb. 22, 1949 

